Diene addition product and process for making it



I Patented Oct. 4, 1949 DIENE ADDITION PRODUCT AND PROCESS I MAKING I'IHoward M. Teeter, Charles R. Scholileld, and

FOR

John C. Cowan, Peoria, 111., assltnors to The United States of Americaas represented by the Secretary of Agriculture No Drawing. ApplicationSerial No. 684,91

Jgly 19, 1946,

. 21 Claims. (01. zoo-4043i (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) This'application is made underthe act of March 3, 1883, as amended by the act of April 30, 1928, andthe invention herein described, if patented, may be manufactured andused by or for the Government of the United States of America forgovernmental purposes without the payment to us of any royalty thereon.

This invention relates to formation of addition products of conjugatedderivatives of polyunsaturated fatty acids with-alpha, beta-unsaturatedcarbonyl compounds. It relates, in partlClllfll',tO 1,4-diene adducts ofalkyl esters of conjugated linoleic acid with crotonic acid nitrile orwith alkyl esters of crotonic acid. It further relates to adducts ofcrotonic acid derivatives with conjugated dienic high molecular weightalcohols, derived by reducing alkyl esters of polyunsaturated higherfatty acids and isomerizing to form the conjugated compound.

One object of this inventionis to provide valuable intermediates for theproduction of high other purposes.

Other objects are apparent from the following specification.

Nonconjugated polyunsaturated fat acids, such as linoleic and linolenicacids, may be isomerized into conjugated forms by several methods; forexample, the methods disclosed by Burr, United States Patent No.2,242,230, or Bradley, United States Patent No. 2,350,583. Neutralderivatives thereof may be isomerized to conjugated forms by the methodof Kass et al., United States patent application Ser. No. 564,500, filedNovember 21,

1944. This method consists of contacting the derivatives with finelydivided metal of group VIII, of the periodic chart of elements,deposited on active carbon black at elevated temperatures, for example,above 150 C.

By neutral derivative is to be understood a derivative not containing afreev carboxyl group,

such as an ester, i. e., a glyceride or an alkyl ester,

tains a plurality of such double bonds'alternated by more than onesinglev bond; for example, 9,12- linoleic acid: 1 V

CH3 (CH2) 4CH=CHCH2CH=CH-(CH 2) ICOOH In many naturally occurringvegetableoils like soybean, corn, and sunflower oils, nonconjugated'rivatives under the conditions described subsequently.

We have found that alkyl esters of conjugated polyunsaturated fat acids,in particular alkyl csters of conjugatedlinoleic acid, may be condensed,by means of an addition reaction, withderivatives of crotonic acid,particularly alkyl 'esters of crotonic acid and crotononit'rile. Theproducts are useful in the production of plasticizers, softening agents,and tackifiers, lubricating oils and additives thereto, and corrosioninhibitors. They are also valuable intermediates in the preparation ofhigh polymeric materials.

Reaction between the conjugated fat acid esters and the crotonic acidderivative is effected byheating and agitating the reactants for 10 to20 hours at 175 to 275 C. in an autoclave under the autogenic pressureso developed. It is convenient to employ a 1.5 to 10.0 molar excess(based I on the amount of conjugated fat acid esters presan alcohol, andso forth. A conjugated polyun- A non-conjugated polyunsaturated fat acidconent) of the crotonic acid derivative. Following reaction, the productis isolated by distillation, whereby the reaction mixture is separatedinto four fractions: (1) recovered unreacted crotonic acid derivative;(2) recovered unreacted conlugated fat acid alkyl ester; (3) theaddition product; and (4) a non-volatile residue which is believed tocomprise polymers of the conjugated alkyl esters admixed with polymersof the crotonic acid derivative.

When certain vegetable oils are employed as a source of linoleic acid,particularly soybean-oil, an intermediate fraction consisting of alkylesters of arachidic acid may be obtained between fractions 2 and 8. Ifdesired, alkyl arachidate may be removed by distillation of the alkylesters prior to the addition reaction.

The first fraction is conveniently recovered by distillation atatmospheric pressure followed by stripping in vacuo. The second fractionis conveniently recovered by fractional distillation at a pressure of 1to 3 mm., and the third fraction is isolated by distillation in ashortpath still at pressures less than 1 mm. The recovered unreactedalkyl ester of the fat acids and the crotonic acid derivative may beutilized for further preparations of the addition product, preferablyafter increasing the amount of conjugation therein by treatmentaccording to the previously mentioned processes of isomerization.

If an isomerization catalyst similar to that of Kass et al., isemployed, it is possible to conduct isomerization and addition of thecrotonic acid derivative simultaneously. For example, nonconjugatedalkyl esters'of the fat acids of semidrying oils are mixed with suitableamounts of isomerization catalyst and crotonic acid derivative, and themixture is sealed in a steel autoclave and processed according to theprocedures outlined above. Strong alkaline isomerization catalysts couldnot be used in this procedure, because crotonic acid and its derivativesare decomposed by heating with strong alkali.

It is believed that the alkyl esters of conjugated fat acids and thecrotonic acid derivative react by 1,4-addition to give the productshaving the following structures I and II. For purposes of illustrationonly, the ester of conjugated fat acids is assumed to be methyl10,12-linoleate. In the formulas, the group R may be, for example,

or CHzOI-I and the group R may be, for example, COzCHs, COzCzHs or CEN.

If esters of nonconjugated polyunsaturated fat acid are present in thereaction mixture as normally will be the case since no existing processof isomerization will completely convert such esters to their conjugatedforms, reaction with crotonic acid derivatives may occur slowly to formproducts which differ from I and II, and which may have the structureIII. For purposes of illustration, the ester of nonconjugated fat acidis assumed to be methyl 9,12-lino1eate. The group R may be, for example,

III

. The product of our invention may be used without further treatment asa plasticizer for synthetic resins, in particular for polyvinyl chlorideand polyvinyl chloride-acetate copolymers. It may also be used as alubricant.

By transesterification of the addition product of ethyl crotonate andconjugated methyl esters of soybean fat acids in the presence of analkaline catalyst, esters of the addition product, such as the2-ethyl-n-hexyl, 2-ethyl-n-butyl and n-octyl esters, may be obtained.These esters may also be prepared by re-esterification with the desiredalcohol of the dibasic acid formed by saponification of the additionproduct or by forming an addition product, according to the proceduresdescribed in this specification, from alkyl crotonates and conjugatedalkyl esters of soybean fat acids wherein the alkyl radicals are2-ethyl-n-hexyl, 2-ethyl-n-butyl, n-octyl, and so forth. In the lattercase, the conditions of isolation and distillation of the product shouldbe modified to take account of the lower volatility of these higheralkyl esters. The higher alkyl esters are valuable lubricants, with orwithout subsequent hydrogenation of their ethylenic unsaturation.

The products, as such, or after saponification or hydrolysis to yieldthe corresponding dibasic acid, are useful for condensation withpolyfunctional alcohols, amines, and so forth, in the production ofpolymeric materials.

The products after reduction of the ethylenic unsaturation therein arealso suitable for use as intermediates in the production of polymers, asplasticizers, as lubricants, and so forth.

If crotonitrile is used as adduct to the ester of conjugatedpolyunsaturated fat acid, the product may be hydrogenated with resultingconversion of the nitrile group to an amino-methyl group. Saponificationof the remaining ester group yields an amino acid which may beselfcondensed to form a polyamide or which may be employed in thepreparation of other polymeric materials.

Alkyl esters of conjugated linoleic acid, either alone or in the form ofalkyl esters of fat acids of conjugated semi-drying oils, may be reducedby well-known means, for example, sodium and alcohol, to thecorresponding alcohols. According to another procedure, alkyl esters ofnonconjugated linoleic acid .or of fat acids for nonconjugatedsemi-drying oils may be reduced with sodium and alcohol to thecorresponding alcohols, and the alcohols may be isomerized to conjugatedforms by treatment with an isomerization catalyst. These alcohols,conjugated linoleyl alcohol and conjugated alcohols of semi-drying oilsmay be employed in addition reactions with crotonic acid derivatives, asdescribed above. The same considerations apply in this case as whenconjugated alkyl esters are employed.

The addition product of such conjugated alcohols and alkyl esters ofcrotonic acid may be saponified to an hydroxy acid which may beselfcondensed to form a polyester, or which may be utilized in thepreparation of other polymeric materials.

aaaapcr ExmuI Methyl esters of soybean oil were treated with anickel-carbon isomerization catalyst, prepared according to thedirections of, Kass et al., United States patent application Ser. No.564,500, for 6 hours at 170 C. The product contained 37.5 percentconjugation as determined spectrophotometricallv. Sixty grams of theconjugated esters was mixed with 86 grams of ethyl crotonate, giving aratio of mols of ethyl crotonate per mol of conjugated material in thetreated methyl esters, and the mixture was sealed in a steel autoclave.After heating and shaking at 245 to 260 C. ior 10 hours, the reactionmixture was cooled, transferred to a still equipped with a concentrictube fractionating column, and distilled in vacuo. Aiter recovery of,unreacted ethyl crotonate, 42.4 grams of unreacted methyl esters wasrecovered. The residue was transferred to a shortpath pot still and bydistillation at 0.5 mm. pressure and 207 to 217 0., 23.9 grams of theaddition product was isolated. The yield was 76.5 percent based on theweight of conjugated esters originally present..

The product was a pale yellow liquid of pleasant odor. Its density was0.9480 at 30 C. its reiractive index at 29 C. was 1.4651; its iodinenumher was 64.6; its molecular weight was 427; and it contained 73.8percent carbon and 10.84 percent hydrogen. The calculated analysis for acompound of structure I or II (R=C02C2Ht) is 73.5 percent carbon, 10.78percent hydrogen, iodine value or 62.0, and molecular weight of 408. Theproduct could be hydrogenated with a platinum catalyst at atmosphericpressure, 475 grams of product being required to absorb 2.016 grams ofhydrogen.

EXAMPLE II An experiment identical to that inExample I was performed,except that the reaction mixture was heated for 20 hours at 185 to188 C.A 58 percent yield of addition product was obtained.

I I Exempt-e111 V In the steel autoclave 45 gramsof methyl esters ofsoybean fat acids, 87 grams of ethyl crotonate and 8 grams of anactivated nickel-carbon isomerization catalyst were heated and shakenfor 10 hours at 220 to 300 C. By the procedure de- Y scribed in ExampleI, 13.6 grams (62 percent of theoretical, calculated upon the assumptionthat the isomerization catalyst produced 35 percent conjugation) of theaddition product, was obtained.

Exmrm IV through a concentric tube iractionating column,

and after recovery of ethyl crotonate, 14.2 grams action mixture, 20.5grams 6 otimreactedalcoholsdistilledatdflmmplessure. The residue wastransferred to a small Claisen flask and distilled at 0.17 to 0.29 mm.pres sure. A yield 01 5.1 grams (38.2 percent) of an addition productwas obtained by collecting the fraction boiling at 228 to 230 C.Anaylsis showed 76.17 percent of carbon and 11.10 percent or hydrogen.The calculated values for a compound or structure I or II n=cmonw colclmare 76.2 percent carbon and 11.18 percent hydrogen.

EXAHPLI V autoclave with 31.7 grams of fresh methyl esters of conjugatedsoybean fat acids. From this reoi 'unreacted crotononitrile wasrecovered.

The residues remaining after recovery of crotononitrile from the tworuns, with the autoclave were combined and distilled. There was obtainedby distillation at 1 to. 5 mm, pressure 43.9 grams of unreacted methylesters of soybean oil, and by distillation at 0.5mm. pressure 21 grams(62.5 percent yield) of anaddition product. 7

The product contained 76.5 percent carbon, 10.77 percent hydrogen,an'd.4.06 percent nitrogen. Its refractive index at 29.7 C. was 1.4749,its density at 30 C. was 0.9488, and its iodine value was 72.3. 1 g

A compound oi structure I or II (R=CN) should contain '76.5 percentcarbon, 10.79'percent hydrogen, and 3.88 percent nitrogemand its iodinenumber should be 70.4.... I

A 20-gram sam'pleofthe addition product obtained in Example I wassaponifled by refluxing 3.5 hours with a solution of 15 grams ofpotassium hydroxide in 60 ml. of ethylene glycol. Etha-, 1101 may alsobe used instead of the *glycol. The product was isolated byacidification and extraction of the reaction mixture, and it was foundto have a neutral equivalent of 185.8. The calculated value for theneutral equivalent of the dibasic acid corresponding to structure I orII (R=CO2C2H5) is 183. I

m... vn

Samples of the addition product obtained in Example I were examined forcompatibility with a variety of commercially useful resins and plastics.Solutions of each resin were prepared which contained 0.25 gram, 0.75gram, and 2.25 grams of resin in 10 ml. of solvent. To each solution wasadded 0.25 gram ofthe addition product. Films were prepared from eachsolution which were inspected for cloudiness, bleeding, or otherindication of incompatibility. The results are shown in the table, wherethe letter C indicates compatibility, and the letter "I", incom- ExnmnnVIII The addition product of ethyl crotonate and conjugated soybeanmethyl esters was compared with dioctyl phthalate as a plasticizer forvinyl chloride (95 percent) -vinyl acetate (5 percent) copolymer. Theformula used for the tests was:

Parts by Resin 63.5 Basic lead carbonate 1.0 Stearic acid, U. S. P 0.5Plasticizer 35.0

After milling and sheeting, physical properties were determined with thefollowing results:

Elongation Heat sta- Min. Plasticizer Compatibilat 1,000 ity bilityflex. pounds Hours 01.7 For comm Addition producL. Com late... 4. to 5.

' Dioctyl phthalate. .....d% 4 0 to 4.5 21 87 EXAMPLE 1x Kinematicviscosity measurements were made upon the addition product of ethylcrotonate and conjugated soybean methyl esters, upon the same substanceafter catalytic reduction of its ethylenic unsaturation with hydrogen,upon several higher .alkyl esters of the addition product, and uponseveral commercial motor oils. The results were as follows:

Kinematic viscosity Viscosity index 100 F. 210 F.

'Additiou product (1) 27.1 4. 06 04. 7 Hydrogenated addition product.28. 6 4. 87 101. 0 Commercial oil No. 1.-.. 4&5 5.22 9.29 Commercial oilNo. 2.... 34 .3 5. 71 117.0 Z-Ethyl-n-hexyl ester of I 34. 8 5. 49 103.0 2-Ethyl-n-butyl ester of 1-. 35. 8 6. 63 105. 0 n-Octyl ester 38. 9 6.21 117. C

The following three examples illustrate the preparation of the catalyst.

EXAMPLE X 192 grams of nickel formate are dissolved in 5,500 ml. of hot,distilled water. The solution is filtered and added to 210 grams ofactivated .carbon. A suitable activated carbon may be prepared fromsulfite wastes resulting from sulfltepulping process by burning at 900C. followed by weight chloric acid, and copiously washing it to removeexcess acids, salts, and other impurities. This suspension is evaporatedby boiling until a 25 to 50 percent moisture content is obtained. The

catalyst composition is then ready for activation by reduction withhydrogen.

Exam XII 24 grams (dry weight basis) of catalyst composition, preparedby the method of Example X, are placed in a 500 ml. three-neckround-bottom flask fitted with a Hershberg stirrer constructed ofnichrome wire, an inlet gas tube reaching as close to the bottom of theflask as possible, a funnel with a. stopcock, a thermometer, and a gasoutlet tube. Hydrogen is passed over the catalyst composition, and thetemperature raised rapidly to about 360 C. The composition is thenstirred intimately with the hydrogen at 360 40 C. for two hours. Thehydrogen is replaced with carbon dioxide, and the flask and contents arecooled to below C. The catalyst may be used immediately or stored invegetable oil under carbon dioxide, nitrogen, or other protective gas.In the reduction of the nickel in the catalyst, other types of apparatuscan be used, but proper precautions must be observed to obtain intimatecontact between catalyst composition and the hydrogen and to excludeoxygen.

Having thus described our invention, we claim:

1. The process of making a 1,4-diene adduct, comprising reacting aconjugated dienic high molecular weight alcohol having the carbonskeleton of a soybean oil fatty acid with ethyl crotonate for 10 to 20hours at to 275 C.

2. A 1,4-diene adduct of an alkyl ester of a. conjugated soybean oilfatty acid with ethyl crotonate the alkyl group having no more thaneight carbon atoms.

3. A 1,4-diene adduct of an alkyl ester of a conjugated soybean oilfatty acid with crotononitrile.

4. A 1,4-diene adduct of a conjugated dienic high molecular weightalcohol having the carbon skeleton of a soybean oil fatty acid and ethylcrotonate.

5. A 1,4-diene adduct of an alkyl crotonate and an ester of the fatacids of conjugated semidrying oils with monohydric alkanols, the alkylgroups each being alkyl hydrocarbon radicals having no more than eightcarbon radicals.

6. A 1,4-diene adduct of an alkyl crotonate and a conjugated dienic highmolecular weight alcohol having the carbon skeleton of fat acids ofsemi-drying oils, the alkyl group of the crotonate having no more thaneight carbon atoms.

'7. A 1,4-adduct of an alkyl ester of 9,11- linoleic acid and an alkylcrotonate, the alkyl group having no more than eight carbon atoms.

neutralizing the resulting c wi hyd o- 75 8. A 1,4-diene adduct of ethylcrotonate and a 9, conjugated dienic alcohol having the carbon skeletonof 9,11-linoleic acid, of the formula:

11 H H n cHrcnm-c-c=c-ccn,).cn,on

x- Y H n in which one of X and Y is CH: and the other is COOC2H5.

9. A 1,4-diene adduct of an alkyl crotonate and a conjugated diene ofthe group consisting of an ester of the fat acids of conjugatedsemidrying oils with a monohydric aikanol, and a conjugated dienic highmolecular weight alcohol having the carbon skeleton of a fat acid of asemidrying oil; the alkyl of the crotonate and of the fat acid estereach having no more than eight carbon atoms.

10. The process of making a 1,4-diene adduct, comprising heating analkyl crotonate with a conjugated diene compound of the group consistingof esters of the fat acids of conjugated semidrying oils with monohydricalkanols, the alkyl groups each'having no more than eight carbon atoms,and conjugated dienic high molecular weight alcohols having the carbonskeleton of fat acids of semi-drying oils, for several hours at about175 to 275 C., and fractionally distilling the reaction mixture in vacuoto separate the 1,4-diene adduct.

11. The process of claim 10, in which the ad duct is isolated bydistillation at pressures less than 1 mm. of mercury.

12. The process of claim 10, in which the coniugated diene compound isproduced in situ from the corresponding unconjuzated diene compound bycarrying out the reaction in the presence of an isomerization catalystwhich does not decompose crotonic acid.

13. The process of claim 10, in which the conjugated diene compound isproduced in situ from the corresponding unconjugated diene compound bycarrying out the reaction in the presence of a neutral isomerizationcatalyst.

14. The process of claim 10, in which the conjugated diene compound isproduced in situ from the corresponding unconjugated diene compound bycarrying out the reaction in the presence of an isomerizing catalystcomprising a nickelcarbon catalyst.

15; The process of making a 1,4-diene adduct comprising reacting analkyl ester of a polyunsaturated soybean oil fatty acid with an alkylcrotonate, by heating in the presence of an isomerizing catalyst thatdoes not decompose crotonic acid.

16. The process of making a 1,4-diene adduct.

comprising reacting a methyl ester of a polyuncomprising reacting analkyl crotonate with an ester of a fat acid of conjugated soybean oiland a monohydric alkanol for several hours at about 176 to 275 0., thealkyl groups each having no more than eight carbon atoms.

20. The process of making a 1,4-diene adduct comprising reacting ethylcrotonate with methyl ester of conjugated soybean oil fat acids forseveral hours at about to 275 C.

21. The 1.4-diene adduct of methyl ester of 9,11-linoleic acid and ethylcrotonate, of the formula:

in which one of X and Y is CH: and the other is -COOC2Hs.

HOWARD M. TEE'I'ER. CHARLES R. SCHOLFIEID.

JOHN C. COWAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,365,363 Swain Dec. is, 19442,375,937 Miller et al. May 15, 1945

